questions regarding shared_from_this

Question

I have a function which takes a shared_ptr. In some member function memfun of MyClass, I need to pass this

Answer 1

The important question here is why does the function take the argument through a shared_ptr. Does it store the pointer internally for later use? Does it only use it for the duration of the call? Why is the ownership diluted among the caller and the callee?

Some answers suggest that you provide a no-op deleter if you are going to pass a stack allocated object into the function, but if the function is actually storing the shared_ptr for later use, it might be the case that by the time it gets around to it, the locally allocated object is no longer in the stack and you trigger UB. Having the no-op deleter shared_ptr will allow the call, but the semantics will not be correct.

If the function does not store the shared_ptr for later use, what was the design decision that led to that API? If you can change the function (and there is no impending reason), make it receive the argument by reference and you will have a friendlier interface that does not impose a shared_ptr for no reason.

If at the end you determine that you can guarantee that the object in the stack will be alive for the whole duration of the process triggered by that function call, then and only then use the no-op deleter.